// Copyright (C) Kumo inc. and its affiliates.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//


#pragma once

#include <pollux/expression/string_writer.h>

namespace kumo::pollux::functions {
    struct ToHexUtil {
        MELON_ALWAYS_INLINE static void toHex(
            StringView input,
            exec::StringWriter &result) {
            // Lookup table to translate unsigned char to its hexadecimal format.
            static const char *const kHexTable =
                    "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
                    "202122232425262728292A2B2C2D2E2F303132333435363738393A3B3C3D3E3F"
                    "404142434445464748494A4B4C4D4E4F505152535455565758595A5B5C5D5E5F"
                    "606162636465666768696A6B6C6D6E6F707172737475767778797A7B7C7D7E7F"
                    "808182838485868788898A8B8C8D8E8F909192939495969798999A9B9C9D9E9F"
                    "A0A1A2A3A4A5A6A7A8A9AAABACADAEAFB0B1B2B3B4B5B6B7B8B9BABBBCBDBEBF"
                    "C0C1C2C3C4C5C6C7C8C9CACBCCCDCECFD0D1D2D3D4D5D6D7D8D9DADBDCDDDEDF"
                    "E0E1E2E3E4E5E6E7E8E9EAEBECEDEEEFF0F1F2F3F4F5F6F7F8F9FAFBFCFDFEFF";

            const int64_t inputSize = input.size();
            const unsigned char *inputBuffer =
                    reinterpret_cast<const unsigned char *>(input.data());
            result.resize(inputSize * 2);
            char *resultBuffer = result.data();

            for (auto i = 0; i < inputSize; ++i) {
                resultBuffer[i * 2] = kHexTable[inputBuffer[i] * 2];
                resultBuffer[i * 2 + 1] = kHexTable[inputBuffer[i] * 2 + 1];
            }
        }

        MELON_ALWAYS_INLINE static void toHex(
            uint64_t input,
            exec::StringWriter &result) {
            static const char *const kHexTable = "0123456789ABCDEF";
            if (input == 0) {
                result = "0";
                return;
            }

            const auto resultSize = ((64 - bits::countLeadingZeros(input)) + 3) / 4;
            result.resize(resultSize);
            char *buffer = result.data();

            int32_t len = 0;
            do {
                len += 1;
                buffer[resultSize - len] = kHexTable[input & 0xF];
                input >>= 4;
            } while (input != 0);
        }
    };
} // namespace kumo::pollux::functions
